From c86c6429538086609114b3a680d59b94dc339bfc Mon Sep 17 00:00:00 2001
From: Nalin Dahyabhai <nalin@dahyabhai.net>
Date: Mon, 22 Jul 2013 16:00:47 -0400
Subject: Notice when read locks fail

When we fail to obtain a read lock on the data, attempt to fail the
operation, so that it can be retried later.
---
 src/back-sch.c | 74 +++++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 50 insertions(+), 24 deletions(-)

diff --git a/src/back-sch.c b/src/back-sch.c
index 9d63c6b..f3ac7d9 100644
--- a/src/back-sch.c
+++ b/src/back-sch.c
@@ -1268,16 +1268,23 @@ backend_search_cb(Slapi_PBlock *pb)
 	if (!slapi_be_exist(cbdata.target_dn)) {
 		slapi_log_error(SLAPI_LOG_PLUGIN,
 				cbdata.state->plugin_desc->spd_id,
-				"slapi_be_exists(\"%s\") = 0, ignoring search\n",
-				cbdata.target);
+				"slapi_be_exists(\"%s\") = 0, "
+				"ignoring search\n", cbdata.target);
 		slapi_sdn_free(&cbdata.target_dn);
 		return 0;
 	}
 	/* Walk the list of groups. */
 	wrap_inc_call_level();
-	map_rdlock();
-	map_data_foreach_domain(cbdata.state, backend_search_group_cb, &cbdata);
-	map_unlock();
+	if (map_rdlock() == 0) {
+		map_data_foreach_domain(cbdata.state, backend_search_group_cb,
+					&cbdata);
+		map_unlock();
+	} else {
+		slapi_log_error(SLAPI_LOG_PLUGIN,
+				cbdata.state->plugin_desc->spd_id,
+				"unable to acquire read lock, "
+				"ignoring search\n");
+	}
 	wrap_dec_call_level();
 #ifdef USE_NSSWITCH
 	/* If during search of some sets we staged additional lookups, perform them. */
@@ -1499,7 +1506,7 @@ backend_check_scope_pb(Slapi_PBlock *pb)
 }
 
 static int
-backend_write_cb(Slapi_PBlock *pb)
+backend_write_cb(Slapi_PBlock *pb, struct plugin_state *state)
 {
 	int ret;
 
@@ -1508,15 +1515,20 @@ backend_write_cb(Slapi_PBlock *pb)
 	}
 
 	wrap_inc_call_level();
-	map_rdlock();
-	if (backend_check_scope_pb(pb)) {
-		slapi_send_ldap_result(pb, LDAP_UNWILLING_TO_PERFORM,
-				       NULL, NULL, 0, NULL);
-		ret = -1;
+	if (map_rdlock() == 0) {
+		if (backend_check_scope_pb(pb)) {
+			slapi_send_ldap_result(pb, LDAP_UNWILLING_TO_PERFORM,
+					       NULL, NULL, 0, NULL);
+			ret = -1;
+		} else {
+			ret = 0;
+		}
+		map_unlock();
 	} else {
-		ret = 0;
+		slapi_log_error(SLAPI_LOG_PLUGIN, state->plugin_desc->spd_id,
+				"unable to acquire read lock\n");
+		ret = -1;
 	}
-	map_unlock();
 	wrap_dec_call_level();
 
 	return ret;
@@ -1527,15 +1539,16 @@ backend_pre_write_cb(Slapi_PBlock *pb)
 {
 	struct plugin_state *state;
 	slapi_pblock_get(pb, SLAPI_PLUGIN_PRIVATE, &state);
-	return state->use_be_txns ? 0: backend_write_cb(pb);
+	return state->use_be_txns ? 0: backend_write_cb(pb, state);
 }
 
 static int
 backend_betxn_pre_write_cb(Slapi_PBlock *pb)
 {
 	struct plugin_state *state;
+
 	slapi_pblock_get(pb, SLAPI_PLUGIN_PRIVATE, &state);
-	return state->use_be_txns ? backend_write_cb(pb) : 0;
+	return state->use_be_txns ? backend_write_cb(pb, state) : 0;
 }
 
 #ifdef USE_PAM
@@ -1623,7 +1636,12 @@ backend_bind_cb(Slapi_PBlock *pb)
 	 * 3. If bind target DN is not found in the map cache, bind request is rejected.
 	 * */
 	wrap_inc_call_level();
-	map_rdlock();
+	if (map_rdlock() != 0) {
+		slapi_log_error(SLAPI_LOG_PLUGIN, state->plugin_desc->spd_id,
+				"unable to acquire read lock\n");
+		ret = 0;
+		goto done_with_lock;
+	}
 	backend_locate(pb, &data, &entry_group, &entry_set);
 	if (data != NULL) {
 		is_nsswitch_origin = slapi_entry_attr_get_charptr(data->e, "schema-compat-origin");
@@ -1669,6 +1687,7 @@ backend_bind_cb(Slapi_PBlock *pb)
 		slapi_ch_free_string(&username);
 		slapi_ch_free_string(&is_nsswitch_origin);
 	} else {
+done_with_lock:
 		map_unlock();
 		wrap_dec_call_level();
 		if (backend_check_scope_pb(pb)) {
@@ -1685,20 +1704,27 @@ backend_bind_cb(Slapi_PBlock *pb)
 static int
 backend_compare_cb(Slapi_PBlock *pb)
 {
-	int ret;
+	struct plugin_state *state;
+	int ret = -1;
+
 	if (wrap_get_call_level() > 0) {
 		return 0;
 	}
 	wrap_inc_call_level();
-	map_rdlock();
-	if (backend_check_scope_pb(pb)) {
-		slapi_send_ldap_result(pb, LDAP_UNWILLING_TO_PERFORM,
-				       NULL, NULL, 0, NULL);
-		ret = -1;
+	if (map_rdlock() == 0) {
+		if (backend_check_scope_pb(pb)) {
+			slapi_send_ldap_result(pb, LDAP_UNWILLING_TO_PERFORM,
+					       NULL, NULL, 0, NULL);
+			ret = -1;
+		} else {
+			ret = 0;
+		}
+		map_unlock();
 	} else {
-		ret = 0;
+		slapi_pblock_get(pb, SLAPI_PLUGIN_PRIVATE, &state);
+		slapi_log_error(SLAPI_LOG_PLUGIN, state->plugin_desc->spd_id,
+				"unable to acquire read lock\n");
 	}
-	map_unlock();
 	wrap_dec_call_level();
 	return ret;
 }
-- 
cgit